Bus transfer apparatus



Jan. 18,1949. K. MAHNKE BUS TRANSFER APPARATUS 2 Sheets-Sheet 1 FiledApril 8, 1948 WlTN ESSESI 5472" 72w. 4%

Jan. 18, 1949. K. MAHNKE BUS TRANSFER APPARATUS Fiied April 8, 1948 A?El E3 Sheets-Sheet 2 INVENTOR K/rr Ma/VMe,

ATTORb/EY Patented Jan. 18, 1949 BUS TRANSFER APPARATUS Kurt Mahnkc,Alden, N. Y., assignor to Westinghouse Electric Corporation, EastPittsburgh Pa., a corporation of Pennsylvania Application April 8, 1948,Serial No. 19,846

9 Claims. 1

My invention relates to bus transfer apparatus for selectivelyenergizing a load from any one of several power sources.

It is an object of my invention to provide bus transfer apparatuscapable of automatically connecting a load circuit to one of three ormore supply sources in a predetermined order of preference. Anotherobject of the invention is to devise such apparatus as a compact andlargely self-contained unit in which the transfer is made by a rotatableselector switch member whose rotation is automatically controlled tooccur in such a direction that the change from a previous to a newconnection passes through a minimum number of intermediate steps.According to a more specific object, my invention aims at devising bustransfer apparatus that connect a load bus to a preferred supply source,an alternate source, an an emergency source in this order of preferenceand depending upon the occurrence of voltage failure of the preferredand alternate sources.

These and other objects, as Well as the means provided by the inventionfor achieving them,

will be apparent from the following description in conjunction with thedrawings which, in Figs. 1 and 2, shows the circuit diagrams of two different embodiments respectively.

In Fig. l the load buses are denoted by Li, L2,

L3, the buses of a preferred power source by Pl, P2, P3, the buses of analternate power source by Al, A2, A3 and the buses of an emergencysource by El, E2 and E3. The load buses and the power supply buses areconnected to the contact terminals of a selector switch S whose movablecontact member is schematically illustrated in developed form. Thecontact member is revolvable in both directions between three activepositions denoted by P, A and E and has an off position betweenpositions P and A and between positions A and E. Three contacts SPconnect the load buses to the preferred buses Pl, P2, P3 when switch Sis in position P. Three contacts SA connect the load buses to thealternate buses Al, A2 and A3 when the switch S is in position A. Threecontacts SE connect the load buses to emergency buses El, E2, E3 whenswitch S is in position E. The contact member of switch S is alsoequipped with three control contacts l, 2, and 3. The particular designof the switch S is of no concern to the present invention. The switchmay be of the drum type so that the elements SP, SA, etc., represent thecontact segments of the switch drum. If desired, however, the switch maybe of the cam type so that then the elements SP, SA, etc., represent thecam members of the switch. The switch member S has its shaft connectedto a gear 4 which is equipped with a hand wheel Si or the like memberfor manual actuation. The gear is also connected to the armature 5 of areversible motor M for automatic performance. The motor has two fieldwindings 6 and l for forward and reverse operation, respectively. Theforward direction of switch movement is indicated by an arrow marked F,and the reverse direction is indicated by an arrow marked R. The motor Mis assumed to be of the capacitor type. The ap pertaining capacitor isdenoted by 8.

The operation of motor M is controlled by a group of interlinked controlcircuits which extend through a common switch 9. This switch is to beclosed when automatic operation is desired. The motor control circuitsare under control by a group of voltage relays PV, AV, EV andappertaining control relays PC, AC and EC.

Voltage relay PV has its coil H connected across the preferred busses PIand P3 and is equipped with two main contacts I2, 53 and two interlockcontacts 14 and X5. Voltage relay AV has its coil I 6 connected acrossthe alternate buses Al and A3 under control by the first interlockcontact I4 of relay PV. Relay AV has two main contacts ll, 18 and aninterlock contact i9. Voltage relay EV has its coil 2! connected acrossthe emergency buses El and E3 under control by the interlock contacts 25and I9 and also under control by a timing relay T. Relay EV has twocontacts 22 and 23.

The contact of timing relay T is denoted by 24 and the appertainingrelay coil by 25. Relay I picks up immediately when energized, but itsdropping out is delayed a relatively long period. This delay may besecured by any suitable timing means, here schematically represented bya dash pot 26.

The control relay PC is electrically associated with voltage relay PVand has a coil 2? for controlling five contacts denoted by 28, 28, Si,32 and 33. Control relay AC is electrically associated with voltagerelay AV and has a coil 34 for controlling five contacts denoted by 35through. 39. Control relay EC is electrically associated with voltagerelay EV and has a coil ll for controlling four contacts denoted by 4-2through 35.

When switch 9 is open, the selector switch S can be moved to any of itspositions by turning the hand wheel 9i. When switch 9 is closed a .dswitch S is in the illustrated off position motor M is energized anddrives switch S to position P. When that position is reached andassuming that the preferred buses Pl, P2, P3 are properly energized, themotor is stopped. The preferred buses are then connected by contacts SPto the load buses Ll, L2, L3. This performance comes about as follows.

Coil H of relay PV is energized as long as proper voltage obtains acrossbuses PI and P3. Hence contacts l2 and l3 close for coil 2'! of relay PCthe circuit Interlock contacts 32 and 33 open and prevent relays AC andEC from. picking up. Contacts 28 and 29 of relay PC close,through'switch d, for armature '3 and forward field winding 6 of motor Mthe circuit Motor M turns switch S in the forward direction. When switchS reaches position P, the motor circuit (2) is opened at contact 2 andthe motor stops. The load buses are now connected through contacts SP tothe preferred buses.

In the event of voltage failure of the preferred source, relay PV dropsout and opens the coil circuit (1) of relay PC so that the motor circuit(2) is additionally interrupted at contacts 2% and 29. If the alternatebuses are under proper voltage, coil It of relay AV becomes energized inthe circuit:

Relay AV picks up and opens its interlock contact F9 for preventingrelay EV from being energized. Relay AV also closes its contacts H andis which energize coil 34 of relay AC in the circuit:

Al-lt-ll-32-34-45-lB-A3 (4) Contacts 35 and 36 of relay AC now close themotor circuit:

Al-M-I 7-3 5-2-6-5-9-3 6-! (l-A3 (5) Motor M is again started in theforward direction and turns switch S to position A. When position A isreached, the motor circuit (5) is opened at contact 2 so that the motorstops. The load buses are now connected at contacts SA to the alternatebuses Al, A2, A3.

When the voltage of the alternate source also fails, relays AV and ACdrop out. Hence the series-connected interlock contacts l5 and i9 ofrelays PV and AV are now both closed and prepare a circuit for coil 2!of relay EV. Timing relay T has its coil 25 energized through contact 3!or contact 3? as long as either relay PC or relay AC is picked upConsequently, relay T becomes deenergized at the moment when relay ACdrops out. Then thepredetermined timing period of relay T startsrunning. At the end'of the timing period the contact 24 of relay Tcompletes for coil 2i of relay EV the circuit:

Assuming that the emergency source is alive, relay EV picks up andenergizes coil 4! of relay EC in the circuit:

Contacts l2 and 53 close a motor circuit through the reverse fieldwinding 1 as follows:

Motor lvi now runs in the reverse direction and turns switch S fromposition A through position P to position E. When position E is reached,the motor circuit (8) is opened at contact 3 so that motor M stops. Theload buses are now connected to the emergency buses.

When switch S is in position E and voltage returns to the previouslydead buses of the preferred source, relay PV picks up and its contact 15opens the coil circuit ('7) of relay EV while causing relays T and PC topick up. Relay PC then re-energizes the motor M with its forward fieldwinding 5 in the above-mentioned circuit (2). Hence, motor M now turnsswitch S from position E to position P and reconnects the load busestothe preferred buses.

When switch S is in position A and power returns to the preferred buses,relay PV picks up, relays AV and AC drop out, relay PC picks up andcloses for motor M a circuit through contact l of switch S:

Pl-l 2-23-i-l-5-53-28-l 3-1 3 (9) lhis circuit includes the reversefield winding 1. Consequently, motor M runs in the reverse direction andturns switch S from A to P Similarly, when switch S is in position E andpower returns to the alternate buses, relays AV, AC and T pick up andrelays EV and EC drop out. Relay AC then closes the motor circuit:

Motor M runs in the forward direction and turns switch S from position Ethrough position P to position A where the motor is stopped by theinterruption of circuit (10) at contact 2. It will be recognized thatthe switch is always turned in the proper direction to connect the loadbuses to the one group of supply buses that ought to be selected.

As mentioned above, the timing relay T has the efiect of delaying theresponse of voltage relay EV so that the emergency source is connectedto the load buses only after a given period of time has elapsed from themoment of voltage failure in the alternate buses. The provision of suchan intermediate timing period is desired when certain switching actionsare to be performed before the newly selected supply bus can be switchedover to the load buses. Depending upon the requirements of eachparticular application, a similar time delay can be provided beforeswitching from the preferred buses to the alternate buses. On the otherhand, the illustrated timing relay T may be omitted if no delayed actionis required. One purpose for which the provision of a timed delay isadvantageous will be exemplified presently.

For some applications, for instance aboard ship, it is desirable thatonly the preferred source and the alternate source are permanently inoperative condition while the emergency source consists of a power set,such as 2. Diesel generator, which has to be started before the loadbuses are switched from the alternate source to the emergency source.The timing period provided by the illustrated relay T can be utilized tosecure a proper starting of the emergency set before the selector switchperforms its switching operation. A circuit suitable for starting theemergency set is exemplified in Fig. 1, although it should be understoodthat other designs of starting circuits may be chosen. According to Fig.l, the relays PV and AV are equipped with additional contacts t6 and M,respectively. Each of these contacts, when closed, connects an auxiliarypower source 48,. such as a battery, tothe pick-up coil of an auxiliarytiming relay U. The contact 49 of relay U, when closed, connects thestarting device ST of the emergency power set to the source 48 undercontrol by a switch 56. Switch iii may be ganged up with switch 9 so asto close when the bus transfer system is set for automatic performance.The timing relay U has a comparatively short timing interval justsuflicient to keep the relay contact itopen during the interval lapsingbetween the opening of contact 48 and the subsequent closing of contact3?. When either the preferred source or the alternate source isconnected to the load buses, the coil circuit of timing relay U isclosed so that the contact 49 is opened and the starting device STdeenergized. When the relay AV drops out, preparatory to the connectionof the load buses to the emergency buses, the timing relay U closes itscontact 49 shortly after the opening or contact 4! but sufiiciently longbefore timing relay '1 closes its contact 33. Thus an interval of timeis available for the operation of the starting device ST which puts theemergency set in operation so that emergency voltage is applied to busesEl, E2 and E3 before switch S turns to position Even though relay T hasdropped out, switch S cannot turn until voltage is available from busesEl, E2 and E3.

It will be recognized that in the embodiment of Fig. l, the selectorswitch S when moving from position E to position A, or from position Ato position E passes through the position P and hence temporarilyconnects the load buses to the preferred buses which are deenergized atthat time. In cases where such a momentary connection is undesirable,the selector switch and the appertaining control system may be designedso that the switch member has its three active positions equally spacedaround the drum with off positions between each neighboring activeposition, and the drum motor may be controlled to rotate always in sucha direction that the transfer is made from any position to any otherposi tion without passing through the unwanted position. To secure sucha control, the bus transfer apparatus according to the invention may beequipped with discriminating relays as exemplified by the embodimentshown in Fig. 2.

In Fig. 2, the load buses and power supply buses are denoted by the samerespective reference characters as in Fig. l. The selector contacts SP,SA and SE of switch S in Fig. to the similarly designated selectorcontacts in Fig. 1. Relays PV, AV, EV, '1, PC, AC and EC as well asmotor M in. Fig. 2 correspond also to the corresponding devices of Fig.1, and the reference numerals between i and 55 applied to the individualelements shown in Fig. 2 designate parts corresponding to the similarlydesignated elements of Fig. 1. Consequently, the design and performanceof the just-mentioned devices of Fig. 2 require no further description.

contrast to Fig. 1, however, two discriminating relays PF and PR. areassociated with the motor circuit controlled by the relay PC. Similardiscriminating relays AR and AF are associated with the motor circuitcontrolled by relay AC, and two discriminating relays ER and EF areassociated with the motor circuit controlled by relay The coils andcont-acts of the discriminating relays are designated by numeralsbetween and (it and will be referred to the following description of theoperation of the system. he switch S is equipped with contacts H throughit which take the place of the control contacts denoted in Fig. l by i,2 and 3.

2 corresponds When the preferred group of buses is under proper voltage,and the switch S in position E with switch 9 open, the coil ll ofvoltage relay PV is energized. Relay contacts I2 and 13 are closed, andinterlock contacts Hi, 15 are open and prevent the other voltage relaysfrom being energized. Coil 21 of relay PC is energized in the circuit:

Pi-l2-2144-32-i3-P5 (11) so that contacts 28, 29 are closed while theinterlock contacts 32 and 33 are open and prevent the relays AC and ECfrom being energized. Nothing further happens as long as switch 9remains open.

When switch 9 is closed, it completes a circuit for coil 5! of relay PFthrough contact ll of switch S:

P i--! 2433-8 I-ES J l-l [-82-9-29-1 3-P3 (l2) Relay PF picks up andcloses at contact 52 the motor circuit:

P li 2-2 8-8 l-52l3- 8 243494 3-P3 (13) Motor M turns the swit h S inthe forward direction so that it passes from position E through Off (2)to position When position P is reac ed, contact ii in switch S opens thecoil circuit (12) of relay PF so that relay contact 52 group of busesand picks up, assuming that these buses have proper voltage. Contacts lland i8 closes and energizes coil 34 of relay AC in the circuit:

Relay AC picks up and closes contacts 35 and 36 which apply voltageacross coil 5'! of relay AF through contact 13 of switch S in thecircuit:

A! -l L! 7-3 5-83- 3--5'6-l 3-B 241-3 6-5 8-A3 (1.5)

Relay AF closes at contact 58 the motor circuit through the forwardfield winding 5 as follows:

Motor M runs in the forward direction and turns switch S from position Pthrough Off (3) to A. When position A is reached, contact 73 openscircuit (15) so that relay AF drops out and opens circuit (16) atcontact 58. The load buses are now connected to the alternate group ofsupply buses.

In the event of voltage failure or the alternate source, relays AV andAC drop out, coil 54 of relay EF is energized through contact '55 ofswitch S, and contact 65 energizes the motor with field winding 6 activeto run the switch S from position A through Oil (I) to position E. Theload buses are then connected to the emergency power source.

Assume that switch S is in position A connecting the load buses to thealternate group of supply buses when proper voltage rte-appears acrossthe preferred buses. Then, the relay PV picks up and opens the interlockcontact i4. As a result, relays AV and AC drop out while relay PC picksup in circuit (11). Contacts 28 and 29 of 7 relay PC now close for coil54 of relay PR the following circuit through contact 12 of switch S:

the alternate to the preferred supply buses.

In a similar manner, the switch is turned directly from position E to Aif the voltage of the alternate supply buses returns while the loadbuses are connected to the emergency supply buses.

It will be recognized that the relays PF, PR, AP, AR, EF, ER and theassociated contact devices H to 1B of switch S represent a directionallydiscriminating control system which operates to run the motor always inthe direction required to pass from any one to another operatingposition without passing through the unwanted position.

It will be understood by those skilled in the art after studying theforegoing disclosure that apparatus according to the invention may bemodified in various respects and may be equipped with individual devicesand circuit elements other than those specifically described withoutdeparting from the objects and principles of the invention and withinthe essential features of the invention set forth in the claims annexedhereto.

I claim as my invention:

1. Bus transfer apparatus, comprising load buses, a plurality of groupsof supply buses, a selector switch disposed for selectively connectingsaid load buses to one of said respective groups of supply buses at atime, a motor in driving connection with said switch, a plurality ofvoltageresponsive relay means connected to said respective groups ofsupply buses and sequentially interlocked with each other so that one ofsaid relay means when active blocks action of the subsequent relay meansand when inactive permits action of the next relay means, a plurality ofcircuits connected to said motor and controlled by said respective relaymeans for energizing said motor when said respective relay means isactive, and a plurality of control contact means disposed in saidrespective circuits and associated, in displaced relation to each other,with said switch so as to deenergize said motor when said switch is inthe position where said load buses are connected to that group of supplybuses whose relay means is active at a time.

2. Bus transfer apparatus, comprising a plurality of groups of supplybuses, load buses, a selector switch having a switch member movablethrough a plurality of positions and having selector contact meansattached to said supply buses and load buses and disposed for connectingsaid load buses to a difierent group of supply buses in differentrespective positions or" said switch member, a motor in drivingconnection with said switch member, a plurality of voltageresponsiverelay means connected to said respective groups of supply buses andsequentially interlocked with each other so that one of said relay meanswhen active blocks action of the subsequent relay means and wheninactive permits action of the neXt relay means, a plurality of circuitscontrolled by said respective relay means and connected between saidmotor and said respective groups of supply buses for energizing saidmotor from one of said groups depending upon which relay is active at atime, and a plurality of control contact means disposed in saidrespective circuits and associated, to each other, with said switchmember so as to open said respective circuits when said switch member isin the one position wherein said load buses are connected with the onegroup of supply buses whose relay means is active.

3. Bus transfer apparatus, comprising load buses, three groups of supplybuses, a selector switch for connecting said load buses to one of saidrespective groups, a first voltage relay having a first coil connectedto a first one of said groups and having first contact means, a firstinterlock contact and a second interlock contact all controlled by saidfirst coil, a second voltage relay having a second coil connected to asecond one of said groups under control by said first interlock contactto be capable of picking up only when said first relay is dropped out,said second relay having second contact means and a third interlockcontact controlled by said second coil, a motor in driving connectionwith said switch, three circuits attached to said motor for energizingsaid motor, one of said circuits being controlled by said first contactmeans to be energized when said first relay is picked up, another one ofsaid circuits being controlled by said second contact means to beenergized when said second relay is picked up, circuit means controlledby said second and third interlock contacts and connected to said thirdcircuit for energizing the latter when said first and second relays areboth dropped out, and control contact means disposed in said respectivecircuits and associated, in displaced relation to each other, with saidswitch so as to open said respective circuits to deenergize said motorwhen said switch is positioned to connect said load buses to that groupof supply buses whose associated one control circuit is energized.

4. In bus transfer apparatus according to claim 3, said circuit meansfor controlling said third motor control circuit comprising a timingdevice controlled by said second relay, and a third voltage relayconnected to said third group of supply buses under control by saidtiming device and having third contact means for energizing said thirdcircuit after the timing period of said timing device has elapsed fromthe drop-out moment of said second relay.

5. In bus transfer apparatus according to claim 3, said three energizingcircuits being connected across said three respective groups of supplybuses.

6. Bus transfer apparatus, comprising load buses, a plurality of groupsof supply buses, a selector switch disposed for selectively connectingsaid load buses to one of said respective groups of supply buses at atime, a motor in driving connection with said switch, a plurality ofvoltage relays connected to said respective groups of supply buses andsequentially interlocked with each other so that one of said relays whenenergized prevents energization of the subsequent relays and whendeenergized permits energization of the next relay, a correspondingplurality of contactor connected to said respective voltage relays to becontrolled by said relays, a plurality of energizing circuits connectingsaid motor with said groups of supply buses respectively under controlby said respective contactors, and a plurality of control contact meansdisposed in said respective circuits and associated, in displacedrelation to each other, with said switch so as to deenergize 9 saidmotor when said switch is in the position where said load buses areconnected to that group of supply buses whose voltage relay is picked upat a time.

'2. In bus transfer apparatus according to claim 6, contactors havingrespective coil circuits connected under control by said voltage relaysto said respective groups oi supply buses to be energized from saidrespective groups, each of said contactors having interlock contacts,and said coil circuit of each contactor extending through respectiveinterlock contacts of the other contactors so that only one of said coilcircuits can be energized at a time.

8. Bus transfer apparatus, comprising load buses, three groups of supplybuses, a selector switch having a member rotatable through threepositions and having contact means disposed to co nect said load busesto said individual respective groups in said respective positions, threevoltage relays connected to said respective groups of supply buses andsequentially interlocked with each other so that one of said relays whenenergized prevents energizer-ion of the subsequent relays and whendeenergized permits energization of the next relay, a reversible motorhaving two energizing circuits for controlling said motor to run inforward and reverse direction respectively, selective control relaymeans having contacts connected to said voltage relays and to saidswitch to be controlled in dependence upon the obtaining position ofsaid switch member and upon which voltage relay is active at the time,whereby said motor is caused to turn in the direction needed to switchsaid load buses from the previously connected group of supply buses tothe group to be newly connected.

9. Bus transfer apparatus, comprising load buses, three groups of supplybuses, a selector switch attached to said load buses and supply busesand having a switch member rotatable through three positions and threesets of contact means closed in said respective positions forelectrically connectin said load buses to one of said respective groupsof supply buses at a time, three voltage relays connected to saidrespective groups of an aly buses and sequentially interlocked with eachother so that one of said relays when energized prevents energization ofthe subsequent relays and when deenergized permits energization of thenext relay, a reversible motor in driving connection with said switchmember and having two energizing circuits for controlling said motor torun in forward and reverse directions respectively, three pairs ofcontrol relays, the relays of each pair being mutually interlocked andhaving two respective control contacts connected with said two circuitsrespectively so that the running direction of said motor depends uponwhich of the two control relays is energized, each pair of controlrelays having two respective coil circuits for controlling saidrespective control contacts, said two coil circuits of each pair beingcontrolled by a different one of said respective voltage relays so thatonly one of pairs is operative at a time, and control means forming partof said switch member being disposed said respective coil circuits forclosing and opening said coil circuits, said control means appertainingto the respective coil circuits of each pair bein angularly displacedrelative to each other and disposed so that in two of said threepositions of said switch member either one of the coil circuits of saidoperative pair of control relays is closed while in the third positionboth coil circuits are open, said third position for the two coilcircuits of each pair of control relays being coincident with the switchportion in which said load are connected to that group of supply buseswhose voltage relay controls the same pair of control relays.

hoses KURT MAHNKE.

No references cited.

